Shock response of single-crystal boron carbide along orientations with the highest and lowest elastic moduli

The response of monocrystalline boron carbide to planar shock loading has been investigated using molecular-dynamics simulations, along crystal orientations with the highest and lowest elastic moduli. While shocks of intensity lower than the Hugoniot elastic limit (HEL) generate quasilongitudinal and quasitransverse waves, an elastic precursor trailed by inelastic waves is observed when HEL is exceeded. Bond breakage, accompanied by temperature rise, is observed to be the primary mode of deformation under the inelastic waves. Higher shock intensities (particle velocity, ${U}_p>2.5\phantom{\rule{0.16em}{0ex}}\mathrm{km}/\mathrm{s}$) generate a deformation shock front, which induces loss of shear strength along with a considerable loss of crystalline order. Boron carbide is also revealed to exhibit two distinct deformation regimes. While shear strength increases with ${U}_p$ in the first regime $({U}_p\ensuremath{\le}2.5\phantom{\rule{0.16em}{0ex}}\mathrm{km}/\mathrm{s})$, a monotonic reduction is observed in the second $({U}_p>2.5\phantom{\rule{0.16em}{0ex}}\mathrm{km}/\mathrm{s})$. The latter regime is also characterized by a convergence in the shock Hugoniot curves obtained along the two loading directions, indicating that the Hugoniot state of boron carbide may be independent of crystal orientation for ${U}_p>2.5\phantom{\rule{0.16em}{0ex}}\mathrm{km}/\mathrm{s}$. Finally, it is shown that the simulation-derived hydrostat curve presented in this work is coherent with experimental data up to 140 GPa and provides an accurate basis for assessing residual strength of boron carbide under shock conditions.